>>>Here is a follow-up to Carl's observations on TOSOUTWi CRONWi in
Jn 14:9. ... It seems clear from this and the other citations
mentioned that the force of TOSOUTWi CRONWi is to mark a point in
time after a considerable period of elapsed time, almost the same as
the dative of extent with comparative adjectives; or to put it
another way, one can almost add the word "after".... The difference
between this and the accusative is subtle, to be sure, but it seems
to be present. <<<

This idea certainly seems to work in the passages cited. In checking
the (mostly) parallel construction in Acts 8:11 to which I referred
in an earlier post, though, the idea didn't seem to me to pan out.
That verse reads "And to him they had regard because that of long
time [hIKANWi CRONWi] he had bewitched them with sorceries." Am I
missing something, or does the expression here indicate simply an
extent of time so that the accusative could have been used with no
difference of meaning at all?

If my reading is correct, the choice of the dative in this particular
context is either a matter of indifference or else depends on some
consideration other than meaning. Unfortunately I don't have my NA26
handy, so I can't check for variants.

By the way, Don, I am the one who questioned the validity of
preferring the harder reading, especially when this canon seems to
predominate over others. I appreciate your comment on the general
character of the MSS. This is a factor that those of us who don't get
to work with the individual MSS at length don't easily see. Our
experience with the MSS is limited to sampling tidbits here and there
where a textual issue arises, and we don't get a chance to gather an
overall impression regarding a scribe's accuracy and care.